Modeling large deformation and failure in manufacturing processes

A state variable model for describing the finite-deformation behavior of metals is proposed. A multiplicative decomposition of the deformation gradient into elastic, volumetric plastic (damage), and deviatoric plastic parts is considered. With respect to the natural or stress-free configuration defined by this decomposition, the thermodynamics of the state variable theory is investigated. This model incorporates strain rate and temperature sensitivity, as well as damage, through a yield surface approach in which the state variables follow a hardening minus-recovery format. The microstructural underpinnings of the model are presented along with a detailed description of the effects which each model parameter has on the predicted response. Issues associated with the implementation of this model into finite element codes are also discussed. The model has been applied in finite element simulations of several manufacturing processes. These include the prediction of anisotropy in hydroforming applications, metal cutting, and high temperature applications such as forging and welding. In each case, experiments are well described by predictions based on this model.